Introduction


Figure 1. Pacific Giant Salamander (Credit: Sierra Nystrom)


Figure 2. The Mack Creek study site is located in the HJ Andrews Experimental Forest, Oregon. (Credit: Dana Warren)


Figure 3. Mack Creek, HJ Andrews Experimental Forest, OR (Credit: Oregon State University)

Data and Methods

Results

Figure 4. Insert Caption

Figure 5. Insert Caption
Channel Class Clear Cut Old Growth
Cascade 247 (55%) 201 (45%)
Pool 31 (41%) 45 (59%)
Side Channel 90 (55%) 74 (45%)

There is not a significant association between forest condition (old growth/clear cut) on where in the channel salamanders are found (pool/side-channel/cascade) for salamanders sampled in 2017. (\(\chi\)2(2) = 5.54, p = 0.063).

There is not enough evidence to conclude that mean Pacific Giant Salamander size in the clear cut section of Mack Creek in 2017 (7.78 \(\pm\) 9.9, n = 368) differed significantly from mean Pacific Giant Salamander size in the old growth section of Mack Creek in 2017 (6.58 \(\pm\) 8.96, n = 327) by a two-sided, two sample t-test (t(692.79) = -1.67, p = 0.096). In addition, the effect size between mean sizes is negligible (Cohen’s d = 0.13).

Figure 5. Insert Caption

Figure 6. Insert Caption

Figure 7. Insert Caption

Mean salamander weight (g) differed significantly between the three creek channel classifications (pool, cascade, side-channel) by a one-way ANOVA test F(2, 684) = 4.22, p = 0.015). However, Post-hoc Tukey’s HSD revealed that only the side-channel and pool channel classifications differed significantly (p =0.0166225). Though mean salamander weight differed significantly between the pool and side-channel sections of Mack Creek, the effect size is small (Cohen’s d = 0.21).

Summary

References

Gregory S. V. 2016. Aquatic Vertebrate Population Study in Mack Creek, Andrews Experimental Forest, 1987 to present. Environmental Data Initiative. https://doi.org/10.6073/pasta/5de64af9c11579266ef20da2ff32f702. Dataset accessed 11/27/2019.